1. Field of the Invention
This invention relates to electrostatically spray painting objects and the booths in which the objects are painted and, more particularly, to a new and improved method of spray painting such objects and new and improved panels used in the spray painting booths to minimize the amount of overspray paint that tends to accumulate on surfaces within the booth.
2. Description of the Prior Art
In electrostatic spray painting of objects, a coating of paint is applied to parts usually in a spray paint booth or enclosure. The parts to be painted may be carried into, through and out of the booth by a conveyor mechanism and the paint is applied by an electrostatic paint applying system. The paint applying system atomizes the paint by converting liquid paint into finely divided paint particles; places an electrical charge on those particles; creates an electrical field between the atomizing device and ground; imparts a velocity to the paint particles so that the particles travel toward the part to be coated; and meters the amount of paint to be applied to the part. The electrically charged paint particles are attracted to and have an affinity for the part to be painted because the part is maintained at ground potential and thereby is at a potential different than that of the paint particles produced by the atomizing device. As a result, an electrical field established between the atomizing device and the part deflects the original trajectory of the charged particles so that they travel in a direction towards the grounded part to be painted.
In an automatic electrostatic system, the atomizing device may be mounted in a fixed position, attached to a gun mover device that provides reciprocating motion or attached to a robot that imparts a predetermined complex motion to the gun. An electrostatic atomizer greatly increases paint transfer efficiency from the gun to the surface to be coated as compared to a non-electrostatic device. Electrostatic systems apply paint at transfer efficiencies (the amount of paint applied to the part as compared to the amount of paint emitted from the spray gun) in the 50%-80% range. Transfer efficiencies rarely, if ever, approach 100%.
The atomized paint that is ejected from the atomizing gun but that does not adhere to the part is sometimes referred to as the overspray. The overspray consists of paint that misses the part or rebounds from the surface of the part being painted and paint particles electrically deflected to surfaces in the spray booth other than the part being painted. For example, such overspray might adhere to metal components of the spray booth and the conveyor mechanism. Most of the overspray is entrained in the spray booth exhaust air. However, a significant amount may become deposited on the spray booth ceiling, conveyor protection components and the conveyor itself. Paint accumulating on these surfaces tend to drop off onto a freshly painted part and thereby causes the part to be rejected. In order to reduce the number of rejected parts, the spray booths must be cleaned periodically such that the amount of time that the spray booth can be used is diminished. The present invention relates to a spray booth in which the amount of overspray that accumulates on surfaces other than the object to be painted is greatly reduced.